Catalyst prepared by homogeneous precipitation under high temperature and pressure

ABSTRACT

A process for preparing a catalyst comprising a metallic catalytic agent on a particulate carrier is disclosed which provides improved uniformity of distribution and fineness of division with narrowness of particle size distribution of the metallic catalytic agent on the carrier. The particles of carrier are suspended by agitation in an aqueous solution of a salt of the metallic catalytic agent and of a source, on heating in aqueous solution, of hydroxyl ions. The suspension is heated in a sealed vessel above 100* C to precipitate the metal or the particles with uniformity of distribution and fineness of division with narrowness of particle size distribution. The metal is converted by conventional procedures to the appropriate active, oxidized or reduced, state. The process is particularly significant with carriers, such as alumina and silica, that in alkaline media are liable to undergo structural charges.

United States Patent Van Beck et al.

[ 51 June 6,1972

I 54] CATALYST PREPARED BY HOMOGENEOUS PRECIPITATION UNDER HIGHTEMPERATURE AND PRESSURE [72] Inventors: Wilhelmus Petrus Van Beek; TheoJan Osinga, both of Vlaardingen, Netherlands [73] Assignee: LeverBrothers Company, New York,

[22] Filed: Apr. 6, 1970 [21 Appl. No.: 26,051

[30] Foreign Application Priority Data Apr. 9, 1969 Luxembourg ..58391[52] US. Cl ..252/440, 252/454, 252/459, 252/455 R, 252/461, 252/466 J,252/473 [51] lnt.Cl. ..B0lj 11/82, BOlj 11/06 [58] Field of Search..252/430, 466 J, 472, 459, 473, 252/440, 454, 461, 455 R [5 6]References Cited UNITED STATES PATENTS 3,207,702 9/1965 Flank et al...252/459 X 3,320,182 5/1967 Taylor et al. ..252/466 J FOREIGN PATENTSOR APPLICATIONS 6,705,259 l0/1968 Netherlands ..252/466J OTHERPUBLICATIONS Gordon et al., Precipitation From Homogeneous Solution,Pub, by John Wiley & Sons, lnc., N.Y., NY. (1959) pages 6- 9 & 43

Primary ExaminerPatrick P. Garvin Attorney-Louis F. Kline, Jr., MelvinH. Kurtz and Edgar E. Ruff [57] ABSTRACT solution, of hydroxyl ions. Thesuspension is heated in a sealed vessel above 100 C to precipitate themetal or the particles with uniformity of distribution and fineness ofdivision with narrowness of particle size distribution. The metal isconverted by conventional procedures to the appropriate active, oxidizedor reduced, state. The process is particularly significant withcarriers, such as alumina and silica, that in alkaline media are liableto undergo structural charges.

5 Claims, No Drawings CATALYST PREPARED BY HOMOGENEOUS PRECIPITATIONUNDER HIGH TEMPERATURE AND PRESSURE The present invention relates to aprocess for the production of a catalyst, which catalyst consists of ametallic catalytic agent in a porous carrier, and to catalysts obtainedin this way.

Catalysts which consist of a metallic catalytic agent in a porouscarrier have been known for many years. They are often referred to assupported catalysts. The efiiciency of such catalysts depends on anumber of properties, such as activity, resistance to poisons,resistance to sintering and selectivity.

it has been found that such properties can be enhanced by usingprocesses for the preparation of the catalyst which improve theuniformity of distribution, fineness of division and narrowness ofparticle size distribution of the catalytic agent in the porous carrier'The activity of catalyst depends primarily on the surface area of thecatalytic agent in relation to weight of catalyst, which surface must beeasily accessible. Uniformity of dis tribution, fineness of division andnarrowness of particle size distribution reduce the likelihood of theparticles of metallic catalytic agent coalescing in the carrier.Coalescing is disadvantageous because it reduces the surface area andhence the activity of the metallic catalytic agent.

Also when for full activity the metallic catalytic agent has to beactivated by reduction, the final activity depends on the amount ofmetallic compound reduced during activation. This quantity depends onthe physical and chemical state, in particular on uniformity ofdistribution and fineness of division, of the metallic compound in thecarrier.

As with activity, resistance to poisons is affected by the surface areaof the catalytic agent. In general the larger the surface area thegreater the resistance to poisons, i.e. the more poison required to makethe catalyst inactive.

Resistance to sintering similarly depends on uniformity of distributionand fineness of division. Resistance to sintering is particularlyimportant when high temperature activation, for example high temperaturereduction, is necessary. Usually the degree of reduction achieved isgreater at higher reduction temperatures. In general with catalysts withhigh resistance to sintering a higher active surface area can beretained than with catalysts whose resistance to sintering is lower.

ln various catalytic processes it is important for the catalyst used tohave a high selectivity. For example, in hydrogenation processes, inwhich two or more double linkages are hydrogenated successively, it isimportant that hydrogenation is carried out in successive stages inorder to obtain partially hydrogenated compounds which are free frommore saturated compounds. This selectivity depends on the structure ofthe catalysts as well as on the nature of the catalytic agent. Thus, forthe selective hydrogenation of triglycerides derived frompolyunsaturated fatty acids, catalysts with a nickel or copper base areoften used, each of which has a specific and different selectivity forthis type of hydrogenation. Usually this selectivity increases with thedimension of the pores of the carrier. When these catalysts areproduced, it is preferred to start with a carrier whose pores have therequired dimension and whose structure is maintained as far as possiblethroughout these operations. Uniformity of distribution, fineness ofdivision and narrowness of particle size distribution aid maintenance ofthe required dimensions and structure.

A great many processes for the preparation of such catalysts mounted oncarriers have been proposed. The most significant proposals can beclassed as follows.

First, processes in which a hydroxide of the catalytic agent isprecipitated from an aqueous solution of one of its salts on to thecarrier in suspension in this solution by the addition of a basiccompound, such as an alkaline carbonate or hydroxide or ammonia. Thenthe carrier bearing the hydroxide precipitated from the aqueous solutionis separated, after which it is washed, if necessary, and dried. Thedisadvantage of such processes is that a significant proportion of thecatalytic agent fails to be precipitated on to the carrier. Furthermore,the quality of the catalysts prepared in this way dependsnot only on thenature of the reagents but also on the way they are added and the pH andtemperature conditions during their addition. it is very difficult,especially on an industrial scale, to obtain catalysts of constantquality.

According to a second type of process, the carrier is impregnated withan aqueous solution of a salt of a metallic catalytic agent, preferablya nitrate, then the impregnated mass is dried and heated to a hightemperature to decompose the salt and form, if necessary afierreduction, the metallic catalytic agent. It has the disadvantage thatduring drying, the aqueous solution containing the salt moves to theouter surface of the carrier so that the catalytic agent is notuniformly distributed in the catalyst obtained.

Both types of process have the disadvantage that it is practicallyimpossible for the catalytic agent to be deposited very finely and withnarrow particle size distribution.

In further proposed processes the metal is precipitated from solution onto the carrier by allowing hydroxyl ions to develop in this solution andnot by adding such ions as above. Netherlands patent application No.6705259 describes such a process in which the precipitation is effectedby heating a suspension of the carrier in an aqueous solution of themetal salt and urea or a similar nitrogen compound. Heating brings aboutthe decomposition of the urea, the pH of the solution is increased bythe effect of the freed ammonia and the metal is precipitated on thesurface of the carrier particles. In such a process evaporation of thesolution can occur and this, it has now been appreciated, leads to lackof uniform distribution over the carrier and only partial attainment offine particle size and narrowness of particle size distribution.

The aim of the present invention is to provide a process which givesimproved uniform distribution and fineness of division with narrowparticle size distribution of the catalytic agent on the carrier.

In general it has been proposed to use a considerable excess of urea, orsimilar nitrogen compound, to metal. It is further aim of the presentinvention to provide a process in which only a small if any excess isrequired.

In Netherlands patent application No. 6705259 it is stressed that thehydroxyl ions should be formed gradually so that the speed at which theagent which is to be precipitated on to the surface of the carrier isconveyed is sufficiently high to avoid the fonnation of precipitationcenters in the solution, this speed of travel being determined by thedegree to which the solution is agitated and by the extent to which thesolid carrier is divided in the suspension. During industrialpreparation of these catalysts in particular, it is important that thereaction time should be as limited as possible, and thereforeprecipitation should be effected as quickly as possible, i.e. thehydroxyl ions should be formed as soon as possible.

On the basis of the criterion specified in the above-mentionedapplication, i.e. that hydroxyl ions should be formed gradually, itmight therefore be expected that, the conditions of agitation of thesolution and the degree of division of the carrier being otherwiseconstant, a faster formation of hydroxyl ions, for example a fasterhydrolysis of the urea, would give a poorer quality catalyst, because inthis case a fraction of the catalytically active agent would beprecipitated in the solution and not on the carrier.

It has now been surprinsingly discovered that the aqueous urea or othernitrogen compound solution can be heated to a temperature which ishigher than the boiling point of the aqueous solution withoutdisadvantageously affecting the final 7 quality of the carrier.

I used, which is very advantageous industrially. Heating the solution ina sealed vessel ensures that water vapor formed does not escape freelythus causing the dessication of the carrier which must beavoided. Thevessel can be sealed in various ways. Thus the vessel can be completelygas-tight, in which case an autoclave or similar apparatus capable ofresisting the high levels of pressure attained must be used.Altematively, sufficient impermeability can be ensured by use of apiston flap valve system or a similar system which allows carbon dioxideor any other gas liberated, for example by decomposition of the nitrogencompound, to be released into the atmosphere. Some steam is of coursecarried along but this release can be limited to a permissible degree byensuring that the valve or piston system closes under a given pressure,for example, by means of a spring.

, The process can advantageously be continuous.

7 Metallic catalytic agent here means a metal that has or promotescatalytic activity in the reduced or oxidized state.

Examples of metals that can be prepared as metallic catalytic agentsaccording to the invention include beryllium, copper, gold, zinc,cadmium, mercury, aluminum, titanium, zirconium, hafnium, germanium,tin, lead, vanadium, niobium, tantalum, antimony, bismuth, chromium,molybdenum, tungsten, manganese, iron, cobalt, nickel, ruthenium,rhodium, palladium, osmium, iridium, platinum, thorium, uranium and rareearth metals. Textbooks and general literature provide'copiousillustrations of further catalysts that consist of metallic catalyticagents in porous carriers. Reference can be made for example toCatalysis", Ed. Emmett, particularly Chap. l, Vol.11, 1955, Reinhold.

Suitable carriers are well known in the literature. Examples includediatomaceous earths (e.g. kieselguhr), pumice, porcelain, silica,asbestos, alumina, charcoal, kaolin, other silicates, infusorial earth,magnesium and barium sulphates and magnesia. Typical surface areas ofsuch carriers lie within the range of 4 to 1,000 sqm/g.

The process of the invention is particularly advantageous for theproduction of catalysts in which the carrier is insufficiently stable inalkaline conditions, as in the case of silica and alumina. In thegenerally acid conditions of the process according to the invention,structural changes in silica and alumina are much less likely than inproposed processes.

Silica or alumina catalysts, useful for instance for the selectivehydrogenation of polyunsaturated triglycerides, should preferably havepores mainly with a diameter of more than 25 A. and preferably more than80 A. A particular advantage of the invention is that catalysts withsuch pore structure can be prepared consistently.

Which salt of the metal to use in the process of the invention is mainlydetermined by the solubility of the salt in water. Water solubilitiesare given, for example, in Handbook of Chemistry and Physics, ChemicalRubber Publishing Co. To prepare catalysts with a high catalytic agentcontent an aqueous solution with a high concentration of a salt of therequired catalytic metal should preferably be used. If no sufiicientlysoluble salts are available, precipitation can be repeated one or moretimes. A second factor which influences the choice of metal salt to beused is if washing of the carrier bearing the metallic catalytic agentis required before drying. In industrial production of catalysts it isimportant to simplify the process as much as possible and therefore notto wash. So a salt should be used which leaves no residue in thecatalyst which could have an adverse efiect on its properties.

It should be noted that the metallic catalytic agent can be a mixture. Acatalyst containing such a mixture can be prepared according to theinvention either by using a mixture of salts or more than oneprecipitation.

.There are many convenient sources of hydroxyl ions. All that isrequired is that hydroxyl ions develop on heating and that the source ofhydroxyl ions is water-soluble. Particularly convenient as sources ofhydroxyl ions are organic nitrogen compounds that hydrolize when heatedin an aqueous medium to form ammonia or primary or secondary amines.Examples of appropriate compounds of this type are urea, but otheramides, such as formamide, dimethylformamide, dimethylacetamide andacetamide, are also suitable.

Compounds which are particularly suitable have the general formula:

where R and R each independently are hydrogen or a C, to C, alkyl groupor, when taken together, are (CH,), (CI-I or (Cl-I O(CH,), X is O or NH;and R is H, or C, to C alkyl group or NRR".

Another substance which can be used to provide hydroxyl ions ishexamethylene tetramine.

The metal is usually precipitated on the surface of the carrierparticles in the form of a hydroxide but sometimes it is preferable toprecipitate it in the form of a basic salt, in which case it isadvisable to see that the solution contains anions of a suitable acid.These anions can be present just as they are in the aqueous solution(e.g. in the form of a catalytic metal salt) or they can be formedduring the same decomposition process which liberates the hydroxyl ions.Basic salts which can be precipitated in this process are, for example,basic iron formate (Ill) in which case the formate ions can for examplebe formed by means of formamide as the source of hydroxyl ions. Becausemetal salts are usually expensive, complete or almost completeprecipitation of the metal is preferred.

Prior proposals have required the use of a considerable excess of thesource of hydroxyl ions to the metal salt. Using a process according tothe invention only slight, if any, stoichiometric excess of source ofhydroxyl ions need be used, i.e. ratio of source to metal from 1 to 4:1,although, of course, larger quantities can be used.

In order to guarantee a sufficiently short reaction time on the one handand maintain the pressure in the apparatus in which heating is carriedout within reasonable limits on the other, it is desirable to select areaction temperature of 1 10 to 250 C and preferably 125 to 200 C.

After the metal has been precipitated on the surface of the carrierparticles, in the form for example of its oxide, hydroxide or basicsalt, it is necessary to ensure that it is in the form in which it bestdisplays the appropriate catalytic activity. Various metals are activein oxidized or reduced state. The appropriate form for each metalcatalyst is very well known as are ways of converting the precipitateinto the appropriate form. Any general inorganic textbook is a suitableguide. In general it will be necessary to dry the carrier containing theprecipitate. As indicated above a washing step prior to the drying stepcan also be included.

Some metals are active as prepared in the oxidized or reduced state butoften an activation step is advisable. Suitable activation processes arevery well known is indicated for instance in Kirk Othmer Encyclopedia ofChemical.

Technology", lnterscience, 1949, Vol. 3, page 267. Examples includethermal treatment at temperatures of to 800 C. and reduction, alsousually at high temperatures, by means of hydrogen or other reducingagents.

Such activation processes can sometimes be performed without anintermediate drying step. Alternatively the carrier particles with theprecipitate can be dried, often after washing, and then activated.Activation can also occur, either of dried carrier or of carrier inwater, in a reaction medium on which the catalyst is to act.

Because of this and because the quality of catalysts ofien diminishesrapidly on storage and because activated catalysts are often pyrophoric,it is often preferable to present the catalysts for storage or for sale,for example, in the non-activated state. The term catalyst used hereintherefore means activated catalyst, catalysts that do not requireactivation before use and non-activated catalysts that requireactivation before use.

It is a particularfeature of the present invention that nickel catalystsso prepared have, surprisingly,.activity in the synthesis of ammonia.Also it is a feature that iron catalysts so prepared have a surprisingactivity in the synthesis of ammoma.

The invention is illustrated by the following examples:

EXAMPLE 1 To a stirred suspension of 50 g of a macroporous silica,having a specific surface of 290 m g, in 500 ml of distilled water, wasadded a-solution of 75 g of nickel nitrate (Ni(NO 6 H 0) and 50 g ofurea in 1,500 ml of water. The suspension obtained was pumped at 700ml/h through a tube, 7.2 m long and with a diameter of 3 mm, which tubewas heated at 180 C. The product was cooled, filtered, washed repeatedlywith water and dried for 16 hours at 90 C. to give a composition havinga, nickel content of 18.2 percent. Activation of this composition wasachieved by reducing it for 4 hours in a tube furnace at 450 C. and in ahydrogen flow at a rate of 60 l/h per g nickel. The properties of thecatalyst are shown in Table 1.

EXAMPLE 2 To a stirred suspension of 50 g of a macroporous silica,having a specific surface of 290 m /g, in 500 ml of distilled water wasadded a solution of 75 g of nickel nitrate (Ni(NO 6 H 0 and 16 g of ureain 1,500 ml of water. The suspension obtained was pumped at 700 ml/hthrough a tube 7.2 m long and with a diameter of 3 mm, which tube washeated at 180 C. The product was cooled, filtered, washed repeatedlywith water and dried for 16 hours at 90 C. to give a composition havinga nickel content of 18.3 percent. Activation of this composition wasachieved by reducing it for 4 hours in a tube furnace at 450 C. and in ahydrogen flow at a rate of 60 l/h per g nickel. The properties of thecatalyst are shown in Table 1.

EXAMPLE 3 To a stirred suspension of 50 g of a macroporous silica,having a specific surface of 290 m /g in 500 ml of distilled water, wasadded a solution of 42 g of vandyl sulphate (V050 5 H 0) and 39.8 g ofurea in 1500 ml of water. The suspension obtained was pumped at 700 ml/hthrough a tube 7.2 m long and with a diameter of 3 mm which tube washeated at 180 C. The product was cooled, washed repeatedly with waterand dried for 16 hours at 90 C.

EXAMPLE 4 After mixing 75 g of a macroporous silica, having a specificsurface of 290 m /g, with a solution of 409 g of nickel nitrate (Ni(NO 6H 0) and 93 g of urea in 635 ml of distilled water, a l l autoclave wasfilled for 75 percent of its volume with the suspension obtained. Whilestirring vigorously the closed autoclave was gradually heated in 66minutes to a maximum temperature of 160 C. during which the maximumpressure observed was 42 atm.

The autoclave was then cooled to 73 C. over 83 minutes after which theimpregnate was removed from the autoclave, washed with hot water anddried for h at 90 C. to give a composition having a nickel content of32.0 percent. Activation of this composition was achieved by reducing itfor 4 hours in a tube furnace at 450 C. and in a hydrogen flow at a rateof 60 l/h per g nickel. The properties of this catalyst are shown inTable 1.

EXAMPLE 5 After mixing 75 g of a macroporous silica, having a specificsurface of 290 mlg, with a solution of 370 g of nickel sulphate(NiSOR 6H 0) and g of urea in 635 ml of distilled water, a 1 l autoclave wasfilled for 75 percent of its volume with the suspension obtained. Whilestirring vigorously the closed autoclave was gradually heated in 33minutes to a minimum temperature of 160 C. during which the maximumpressure observed was 42 atm.

The autoclave was then cooled to 48 C. over 131 minutes after which theimpregnate was removed from the autoclave, washed with hot water anddried for 132 h at 90 C. to give a composition having a nickel contentof 38.0 percent. Activation of this composition was achieved by reducingit for 4 hours in a tube fumace at 450 C. and in a hydrogen flow at arate of 60 l/h per g nickel. The properties of this catalyst are shownin Table 1. Because of sulphate left after the washing step the catalystcontained 1.6 percent sulphur based on weight of nickel.

EXAMPLE 6 In a 2-liter stainless steel autoclave, equipped with anefficient magnetic agitator, a temperature reading device for theinterior of the autoclave and a cut-ofi' cock, were fed successively:

25 g of spherical amorphic silica with a specific surface of 170 sq.rn/g75 g of nickel nitrate (Ni(NO 6 H 0) g of urea 750 ml of distilledwater. After closing the autoclave and starting up the agitator, theautoclave was heated as quickly as possible until its internaltemperature was about C. and this temperature was maintained for about45 minutes while continuing to stir. After cooling to a temperature ofabout 50 C. and releasing the pressure, the autoclave was opened. Thestill hot suspension was filtered and the filter cake washed severaltimes with water after which it was dried for 16 hours at 200 C. inorder to obtain a composition with a nickel count of about 19.4 percent.The compound was activated for 4 hours at 450 C. in a current ofhydrogen. The catalyst obtained had the following properties:

Specific surface of nickel(determined according to the technique of J.W.E. Coenen, Delft thesis 1918):

260 sq. m/g of nickel Degree of reduction (reduced Ni ratio total Ni,according to the technique of B.G.Linsen, Delft thesis, 1964) 78.5percent Activity benzene (number of millimoles of benzene converted perminute and per g of nickel during hydrogenation of gaseous benzenecontrol conditions): 3.2. Average granulometry (determined by hydrogenchemisorption) 25 A.

Table 11 gives further examples of supported catalysts that can beprepared according to the invention and reactions which the catalystscan be used to catalyze.

TABLE II Metallic catalytic lreeipi- Example agent Carrier tant SaltExmnplo ol' venetian catalyzed 7 Cobalt Alumina Urea C(N03)z.6IIzOHydrogenation. 1 7

Magnesium 8 ..do Hydroxide .do C0(NO )1.6HO..... Reduction CarbonateNKNO) 6H 0 3 2. z 9 mn/nlckel S "{Fe(N0 )r.0H O N +3II -+2NH;

Chromium (oxide) Alumina. do.'- CrCla Dehydrngenation. 3 11 1"Rant enium.do -do R1101: Ce+ lg- CII4 12 .ififigffgffiffff? -:}si1ica -do crnon-urono 13 Ti sufi. Alumina do 8 0884.56. Oxidation. 6

ilOXl 8 ll 2.2 2 14 }S1llca d0 04 i Do. 1 15 .IAIlz10: D.(i .ia do .doA12(S04)3 Oll washing. 16 ;g %f .do .do Acroleln nerylonitrilo.

{Molybdenum do do (a) nc do ...do.. -t ..d0 J10 13080421110 io -de ..{gggg ,gg ,gg- :}0xldntlon 0min. Alumina do CdCl2.HrO. Fatty alcohols fromfatty acids .do C0(N0a)2.6Hz0 Hydrogenation.

do {Co(NOa)z.6Hi0. gnfigagz-ggnou 0 a 2. 2 Urea Cr(NO3)3 9H2}Hydrogenat1on.

do Er(NOa)2 61120-- DMA Fe(NO3)a9H2 C0 H2O 002 H2 DMF Fe(NO 9H20 ZnCOaUrea 3538:. }Dehydrogenatlon. Silica ..do HiOCl .8H O Cracking ofhydrocarbons.

.. d0.. .d0 GB,(N 3)2...

do. .do MnF Oxidation. Kaolin d Ni(N0a)2 61120 CO CH4 Silica..." HMTNi(NOa)z.6H2O. Asbestos Urea Ni(NO3)2.6H20

Silica "go l1iJ((I I II% ))4.%II-If% Fischer-Tropsch- Synthesis ofmethanol.

Pressure hydrogenation of fuels. Dehydrogenation.

. Catalytic reforming.

. Pressure hydrogenation of coal. Oxidation of ethylene.

1. After activation at 500 C. for 4 h with hydrogen such a catalyst ismore active for the hydrogenation of benzene than a catalyst prepared byboiling an ammoniacal solution of cobalt nitrate to precipitate thecobalt in an alumina'support.

2. For example reduction of azelaic acid dinitrile in ammonia andhydrogen.

3. For-example conversion of cyclohexane or n-hexane to benzene.

4. A solution obtained by reducing Na,MoO with iron an HCl and thenfiltering err excess iron is used.

5. Such a catalyst after activation at 500 C. for 4 h in air gives amuch higher conversion rate per unit weight molybdenum than a commercialcatalyst.

6. For example in the oxidation of o-xylene such acatalyst is moreselective than a commercial catalyst.

7. For example in the oxidation of toluene to benzoic acid such acatalyst after activation is more selective and more active than a tinvanadate catalyst prepared according to J .K.Chowdhury andS.C.Chowdhury, J .Indian Chem.Soc., 11, 194 (1934).

8. A solution of Na MoO is reduced with zinc and filtered.

To the filtrate is added Cr( NO, ),.9H,O.

9. 'A filtrate after reduction of Na,MoO with zinc is used.

10. A filtrate after the reduction of Na,WO with zinc is used.

1 l. Dimethylacetamide.

l 2. Dimethylfonnarnide.

l3. Hexamethylene tetramine.

We claim:

1. A process for preparing a catalyst, said catalyst consisting of ametallic catalytic agent on a particulate carrier selected 40 from theclass consisting of diatomaceous earthes, pumice,

porcelain, silica, asbestos, alumina, kaolin, infusorial earth,magnesium sulphate, barium sulphate and magnesia in which process 1.particles of said carrier are suspended by agitation in an aqueoussolution of a. a water-soluble salt of the metallic catalytic agent, and

b. a source of hydroxyl ions selected from the class consisting ofhexamethylene tetramine, urea, formamide, dimethyl formamide, acetamideand dimethyl acetamide which on heating in aqueous solution develophydroxyl ions; and

2. said particles in said aqueous solution are heated in a sealed vesselto between 110 C. and 250 C. to develop sufiicient hydroxyl ions toprecipitate the metal on the surface of said particles so that, onconversion of the metal to the active, metallic catalytic agent, formsaid metallic catalytic agent is distributed uniformly and in a finelydivided state with narrow particle size distribution on the carrier.

2. A process as claimed in claim 1 in which the particles in the aqueoussolution are heated in the sealed vessel to between 125 C. and 200 C.

3. A process as claimed in claim 1 in which the mole ratio of saidsource of hydroxyl ions to said metal is between 1 l and 4: l.

4. A process as claimed in claim 1 in which the particulate carrier isselected from the class consisting of silica and alumrna.

5. A process as claimed in claim 1 in which themetallic catalytic agentis nickel.

ranian-

2. said particles in said aqueous solution are heated in a sealed vesselto between 110* C. and 250* C. to develop sufficient hydroxyl ions toprecipitate the metal on the surface of said particles so that, onconversion of the metal to the active, metallic catalytic agent, formsaid metallic catalytic agent is distributed uniformly and in a finelydivided state with narrow particle size distribution on the carrier. 2.A process as claimed in claim 1 in which the particles in the aqueoussolution are heated in the sealed vessel to between 125* C. and 200* C.3. A process as claimed in claim 1 in which the mole ratio of saidsource of hydroxyl ions to said metal is between 1 : 1 and 4 :
 1. 4. Aprocess as claimed in claim 1 in which the particulate carrier isselected from the class consisting of silica and alumina.
 5. A processas claimed in claim 1 in which the metallic catalytic agent is nickel.